Method for toning a latent image

ABSTRACT

This specification shows and describes the general arrangement of an electrostatic copy machine, and illustrates the principle of cloud formation toning which is the novel element of the machine. The toner is semi-conducting and is positioned between oppositely charged electrodes. The surface of the toner pile will take on the charge of the electrode upon which it rests, and the top surface toner particles will be attracted to the top electrode. The top electrode is a screen. Some of the particles will attain enough speed and alignment to be able to continue through the mesh of the screen. The like-charged particles which do pass the screen will then repel one another and move about in an agitated cloud. These particles may be attracted to a charged image on a sheet carrier if the charged area is of opposite polarity. If of the same charge polarity, and an opposite bias on a field plain behind the charged image, then the background will attract the toner, and the image will repel the toner.

United States Patent [191 Raschke [111 3,865,609 [451 Feb. 11, 1975METHOD FOR TONING A LATENT IMAGE [75] Inventor: Curt Robert Raschke,Warrensville Heights, Ohio [73] Assignee: Addressograph-MultigraphCorporation, Cleveland, Ohio [22] Filed: Jan. 30, 1974 211 App]. No.:437,949

[52] US. Cl ll7/l7.5, 118/637 [51] Int. Cl. 603g 13/08, 603g l5/08 [58]Field of Search 117/175; 118/637; 96/1 R,

96/1 SD; 355/3 D, 3 P; IOl/DIG. l3

[56] References Cited UNITED STATES PATENTS 2,758,525 8/1956Moncrieff-Yeates ll7/l7.5 3,011,473 l2/l96l Gundlach ll7/l7.5 3,057,997lO/l962 Kaprelian ll7/l7.5 3,178,281 4/1965 Jarvis 96/l.2 3,232,1902/1966 Willmott ll7/l7.5 3,420,168 l/l969 Johnson.... 3,470,009 9/l969Gundlach.. 3,518,969 7/1970 Snelling 3,789,753 2/1974 Rutherford lOl/lPrimary Examiner-Michael Sofocleous Attorney, Agent, or Firm-Ray S. Pyle[57] ABSTRACT This specification shows and describes the generalarrangement of an electrostatic copy machine, and illustrates theprinciple of cloud formation toning which is the novel element of themachine.

The toner is semi-conducting and is positioned between oppositelycharged electrodes. The surface of the toner pile will take on thecharge of the electrode upon which it rests, and the top surface tonerparticles will be attracted to the top electrode.

The top electrode is a screen. Some of the particles will attain enoughspeed and alignment to be able to continue through the mesh of thescreen. The like-charged particles which do pass the screen will thenrepel one another and move about in an agitated cloud. These particlesmay be attracted to acharged image on a sheet carrier if the chargedarea is of opposite polarity. If of the same charge polarity, and anopposite bias on a field plain behind the charged image, then thebackground will attract the toner, and the image will repel the toner.

3 Claims, 2 Drawing Figures 1 METHOD FOR TONING A LATENT IMAGE SUMMARYOF THE INVENTION The purpose of the invention is to produce a cloud ofcharged toner particles, which are then available for any purpose.

It is one object of this invention to use such toner cloud to tone anelectrostatic image.

The cloud may be produced in any polarity.

Therefore, it is a further purpose, and object of this invention, toprovide a reversible charge formation device, in order that a backgroundbias behind a carrier with an image charge will cause the image to repelthe toner and the background to attract the toner.

BACKGROUND OF THE INVENTION An electrostatically produced latent imageon a sheet, whether a single copy ofa page, or one in a series ofduplicated reproductions, is made visible by first attracting visibleparticles, known as toner, to the electrostatic charge for a temporarydevelopment of the image. Thereafter the toner is fixed to the sheetupon which the charge is carried, or transferred to a final sheet andthen fixed. The latter option is used for making plain paper printswithout the need for special coatings on the paper.

In the art, toning has been done by dusting, cascading, magnetic brushapplication, and liquid suspension. Dusting by a cloud of chargedparticles has been proposed and attempted often. Carlson, US. Pat. No.2,815,734, shows an early attempt to tone from a cloud and Xerox, US.Pat. No. 3,646,910, shows that the search continues, but with the airblower concept now quite commonly shown in literature, but seldom usedin commerce.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration of the essentialelements of an electrostatic copy machine, embodying acloud tone of thisinvention.

FIG. 2 is a schematic illustration of a cloud toner for a machine as inFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT .The drawings illustrate anapparatus of novel construction which is suitable for carrying out thenew and novel method disclosed herein.

An intake into the electrostatic copier machine will accept originaldocuments to be copied. The term original document may -be applied to adocument which was prepared for some primary purpose other than to be amaster for duplication. A business letter is an example. Or, theoriginal document may be a specially prepared original intended for thepurpose of being a master. A news bulletin, for example. In the instancewhere the machine is to be used as a duplicator, such a master simplyprovides the source material from which a long series of identicaloriginals is produced. The difference between a copy machine and aduplicator is primarily one of speed and repetition.

In the FIG. I, which is intended to illustrate a copy machine more thana duplicator, a belt 11 is shown as a transport device to take anoriginal document from the intake 10 into the field of the opticalsystem. Pinch rolls 12 are used as intake feed rolls and pinch rolls 13are used as exit feed rolls. The original document is either brought toa halt in the field of the optical system, .or a proper optical systemwill be enabled to make a fully acceptable exposure as the documentcontinues in motion.

A corner 14 beyond the pinch rolls 13 will cause the document to turnand drop into a receptacle tray 15 where it may be recovered.

The optical system is illustrated by means of mirror 18, lens 19 andmirror 20 for projecting an image of the original document on the'belt11 into an exposure station within the machine.

Photoconductive paper 22 is shown in a roll stored within the machine,and fed over a series of roller 24 in a feed system to the output of themachine.

A corona 26 is placed to flood the surface of the paper 22 with chargedion particles to produce a uniform charge on the surface of the paper asit is fed from the roll storage to the exposure station indicated byreference character 27. At station 27 the light and dark image willdischarge the surface where light strikes.

The rollers 24 direct the charged and exposed paper 22 to a tonerstation 28 where a cloud of toner bearing a charge opposite that placedon the surface of the paper 22 by the corona 26 is caused to beattracted to the charge remaining on the paper and produce avisibleimage.

The toner material is conveyed by a supply system 29 to the surface of aconveyor belt 30 where it is trans ported through the toner station 28and then returned to a sump 31 for recirculation.

A layer of toner 32 is transported on the surface of the belt 30 into aposition below a screen 34, see FIG. 2. The belt 30 is composed ofconductive material, preferably metal, and the screen 34 is of open meshconstruction and is also conductive and preferably of metal.

A field plate 36 provides a backing for the paper 22 in the tonerstation 28.

In FIG. 2, the reference character 38 indicates a group of markssuggesting a positive charge in image configuration Production of such acharge on the surface of paper 22 is old and well-known and does notconstitute part of this invention. The FIG. 1 apparatus is merely asuggestion of one possible means for obtaining a charge in imageconfiguration upon the surface of some carrier. In this instance, acoated paper 22 is used and the coated paper 22 is toned and fixed andthen serves as the final product.

Power supply 40 illustrates an application of high voltage potentialbetween the screen 34 and the belt 30.

This invention is embodied principally in the construction and operationof the elements 30 and 34 in harmony with the layer of semiconductingtoner particles 32. However, the cloud of toner that can be produced bythese elements is useless unless utilized by an output which consumesthe cloud. The paper 22 is one example of that output and the fieldplate 36 assists the paper 22 in making use of the output.

The method of producing a cloud of charged toner particles, anddeveloping an electrostatic image from the cloud, comprises the steps ofestablishing a base electrode, which in this case is the conductingmetal belt 30. The base electrode of necessity is oriented in aconfiguration to support a quantity of pulverized toner particles 32. Inthis embodiment the particles are transported through the toner stationbut an occasional replenishing and vibrating system may also beemployed.

In the process, the screen 34 functions as a screen electrode which issuperposed with the base electrode, and a high voltage is imposed havingopposite polarity between the base and the screen electrodes.

Then, by supplying a semiconductor layer of toner particles 32 upon thebase electrode 30, the surface particles of the layer of toner will takeon the polarity of the base 30 and thereby be attracted to the screen 34of opposite polarity.

It is understood that many of the particles will lift away from the bodyof the toner supply and migrate rapidly toward the screen 34. Some ofthose particles will strike the screen and be neutralized and thenreturn to the body of the supply 32 but others will manage to passthrough the mesh of the screen to circulate as a cloud above the screen.

Therefore, when the carrier in the form of paper 22, which has anelectrostatic image of a polarity the same as the screen, is moved intosuperposed registration over the screen, the image is immersed in thecloud that is formed by the particles which pass through the screen.

Then, the particles which do pass through the screen, being all of likecharge, will be an agitated cloud and will seek an opposite charge suchas the charge 38.

ln the FIG. 2 illustration, the belt 30 will have a negative charge andthe screen a positive charge. The toner particles which move towards andthrough the screen will then have a negative charge and will beattracted to the positive charge in the image configuration 38 on thepaper 22.

This invention is essentially a toner process and construction of tonerequipment. It will tone any charged surface. Therefore, if a dielectricsurface is charged in an image of a document to be reproduced, and movedinto the toner cloud, it will be toned. That toned image can thereafterbe transferred to plain paper by contact under pressure, or if the toneris magnetic as well as semi-conducting, a magnetic roller may be used toassist in the transfer. These are known techniques and do not enter intothe toner invention.

For illustration purposes, FIG. 1 provides coated photoconducting paper22, which after toning is passed by roller 42 to a fusing and cut-offdevice indicated by reference 44 before being transported through exitconveyor 45 to a tray 46.

What is claimed is:

l. The method of producing a cloud of charged toner particles, anddeveloping an electrostatic image from the cloud, comprising the stepsof:

a. establishing a base electrode in a configuration to support aquantity of pulverized particles b. establishing a screen electrodesuperposed with said base electrode c. imposing a high voltage ofopposite polarity between said base and screen electrode d. providing asupply of pulverized semi-conducting toner particles upon said baseelectrode, whereby the surface particles of said supply take on thepolarity of said base and are thereby attracted to said screen of opposite polarity, some being neutralized by said screen to return to saidsupply, and others passing through said screen to circulate as a cloudabove the screen; and

e. moving a carrier having an electrostatic image into superposedregistration over said screen with said image immersed in said cloud tothereby attract toner to the carrier in a pattern according to theimage.

2. The method as defined in claim 1, wherein step (e) is furthercharacterized in that the polarity of the image is the same as thescreen; the cloud thereby being of opposite polarity and attracted tothe image.

3. The method of producing a toner cloud according to claim 1, furthercharacterized by providing a bias field on the back side of saidcarrier, and establishing said screen and bias oflike polarity, wherebysaid cloud will be of a polarity the same as the image and will beattracted to the background.

' l l= l

1. THE METHOD OF PRODUCING A CLOUD OF CHARGED TONER PARTICLES, ANDDEVELOPING AN ELECTROSTATIC IMAGE FROM THE CLOUD, COMPRISING THE STEPSOF: A. ESTABLISHING A BASE ELECTRODE IN A CONFIGURATION TO SUPPORT AQUANTITY OF PULVERIZED PARTICLES B. ESTABLISHING A SCREEN ELECTRODESUPERPOSED WITH SAID BASE ELECTRODE C. IMPOSING A HIGH VOLTAGE OOFOPPOSITE POLARITY BETWEEN SAID BASE AND SCREEN ELECTRODE D. PROVIDING ASUPPLY OF PULVERIZED SEMI-CONDUCTING TONER PARTICLES UPON SAID BASEELECTRODE, WHEREBY THE SURFACE PARTICLES OF SAID SUPPLY TAKE ON THEPOLARITY OF SAID BASE AND ARE THEREBY ATTRACTED TO SAID SCREEN OFOPPOSITE POLARITY,SOME BEING NEUTRALIZED BY SAID SCREEN TO RETURN TOSAID SUPPLY, AND OTHERS PASSING THROUGH SAID SCREEN TO CIRCULATE AS ACOLD ABOVE THE SCREEN, AND E. MOVING A CARRIER HAVING AN ELECTROSTATICIMAGE INTO SUPERPOSED REGISTRATION OVER SAID SCREEN WITH SAID IMAGEIMMERSED IN SAID CLOUD TO THEREBY ATTRACT TONER TO THE CARRIER IN APATTERN ACCORDING TO THE IMAGE.
 2. The method as defined in claim 1,wherein step (e) is further characterized in that the polarity of theimage is the same as the screen; the cloud thereby being of oppositepolarity and attracted to the image.
 3. The method of producing a tonercloud according to claim 1, further characterized by providing a biasfield on the back side of said carrier, and establishing said screen andbias of like polarity, whereby said cloud will be oF a polarity the sameas the image and will be attracted to the background.